Flow sensor based on electrical capacity

ABSTRACT

An electric measurement method and apparatus for detecting a mass by an electric capacity (permittivity) or a material&#39;s dielectric constant, or alternatively, electric inductance (permeability). The mass may be any phase or combination of phases. The mass may be stationary or flowing. It may comprise discrete particles such as grain, or manufactured products such as ball bearings or threaded fasteners, etc. The mass may be a flow element in a rotameter or similar flow measurement device. The sensor comprises a volume which may be completely full or only partially full of the material. The material may be discrete components or a continuum. Sensor signals may be received by existing planter monitoring systems. In some embodiments the flow sensors are positioned external to the application port. In some embodiments sensors may be utilized which are responsive to the refractive index variation of specific chemicals.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of and claims priority ofU.S. Ser. No. 14/037,680, filed Sep. 26, 2013. The entire contents ofU.S. Ser. No. 14/037,680 is incorporated herein by reference in itsentirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates generally to a flow sensor. Moreparticularly the present invention relates to a method and apparatus forsensing the flow rate of fluids, granular solids, and discrete particlesby measuring electrical capacity for dielectric materials and magneticpermeability for magnetic materials.

Background Art

The dielectric constant of a first material is usually different thanthat of a second material. The dielectric constant for a substance mayvary depending on the thermodynamic state of that substance, such as itsstate: solid, liquid, or vapor (gas). Therefore, the presence of amaterial may be detected by a process by which its effective dielectricconstant is determined. The state of that material may also be deducedfrom the value of the effective dielectric constant. Similarly, formagnetic material, the presence of a material may be detected by aprocess by which its effective relative permeability is determined. Thestate of that magnetic material may also be deduced from the value ofthe effective relative permeability of the material.

Anhydrous ammonia is a popular choice for providing nitrogen tocrops—particularly corn—in the Midwest. Other forms of nitrogen areapplied in liquid form, both during planting and as a side dressing.

For a state such as Iowa, the average annual export of nitrate fromsurface water in Iowa was estimated to range from 204,000 to 222,000 Mg,or about 25% of the nitrate the Mississippi river delivers to the Gulfof Mexico, despite Iowa occupying less than 5% of its drainage basin [K.E. Schilling and R. D. Libra. Increased baseflow in Iowa during thesecond half of the 20th century. Journal of American Water ResearchAssociation, 39:851860, 2004]. Therefore, controlling the flow rate ofanhydrous and other nitrogenous fertilizers is paramount to avoidingnitrification of surface and ground water.

Iowa State University published an article describing the difficultiesof anhydrous ammonia application entitled, “Improving the uniformity ofanhydrous ammonia application,” Publication Number PM 1875, dated June2001. This publication is hereby incorporated in its entirety byreference.

When insufficient anhydrous ammonia is applied to a crop row, that fieldstrip (area) will not yield as it should and the costs incurred fromtillage, planting, and harvesting are an economic disadvantage. Again,controlling the rate of application is crucial for the production offood stuffs on the farm.

Sensing the flow of anhydrous ammonia is one application of the sensorof the present invention. U.S. Pat. Nos. 6,208,255 and 6,346,888, bothof which are hereby incorporated by reference, discuss how to use nearresonance microwave techniques for flow measurements. Most row-cropagricultural equipment for the application of anhydrous ammonia is notprovided with flow sensors for individual rows. Additionally, liquidspray agricultural equipment does not provide for individual rowsensing.

Considering anhydrous ammonia application systems, present single-sensorsystems measure mass per acre but row to row variations can run as muchas 30%. Present day anhydrous ammonia applicators use cooling towers orcooling chambers and pressurized systems or combinations of the two. Onecommon system used has cooling towers or devices that use bleed off of 5to 10% of the ammonia vapor for liquefying the remaining anhydrousammonia. The bled vapor is often injected along with the measuredammonia resulting in over-application. Also, after the liquid anhydrousammonia leaves the cooling chamber and flow sensor, vaporization mayagain occur. This results in varying rates of application due to manyfactors such as heating of the applicator hoses. In order to keep theflow rate to each row similar, often identical length hoses are used.Hoses for short distances are coiled while hoses for longer distancesare straighter. However, unless the hoses are held parallel to ground,anhydrous ammonia liquid will pool in low regions resulting indifferential flow rates. Also there is no easy way to tell if the hoseon a particular row is plugged because the rate controller keeps thetotal rate constant even if an individual hose is plugged.

Totally pressurized systems for anhydrous ammonia are available andprovide liquid flow through the flow sensor system. However, thesesystems are more costly and require more maintenance. They also do nottypically have row plugging detection. Augmenting such systems (hybridsystems) with delivery pumps to maintain pressure for higher rates iscostly, as well as more complex, resulting in poorer reliablity.

Anhydrous ammonia applied by a typical system is nominally 90% vapor and10% liquid by volume, but nominally 90% of the mass of the appliedammonia is in the liquid form. These properties make flow sensingchallenging.

Sensing the flow rate of particulate matter, such as grain has proven achallenge as well. Inaccurate sensing of individual grains in a plantercan result in overpopulation or sparse planting—neither of which isadvantageous to the farmer.

Poor measurement of other substances may have alternate adverse impactsin other applications. It is therefore very advantageous when a flowmonitoring systems can detect non-uniformity of flow and, whereapplicable, is used to control and/or adjust flow uniformity.

There is, therefore, a need for an improved method and apparatus forsensing fluid flow—liquid, vapor, or solid, or a mixture—to provide foruniform application of the fluid.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to provide a method and apparatusfor sensing fluid and particulate flows. An additional object of thisinvention is to measure the mass of a material whether the material isstationary or flowing. An additional object is to provide a flow sensingsystem that does not require cooling towers or other phase- changeapparatuses to effectively sense flow rate. Still another object is todetect a path traveled by a particle such as a single grain or a bubblewithin a liquid.

A measure of the presence and amount of a substance in a specifiedvolume can be made by measuring the capacity between two electricalconducting plates positioned on the periphery of that volume. It is notnecessary that the plates be directly opposed to one another. However,for example, a volume consisting of a rectangular cross section (onelong side and one shorter side) could have electrical conducting platesalong each long side and electrical non-conducting plates along theshorter sides. The surfaces on the third dimension of the volume areusually such that the substance to be measured could move into and outof the volume.

In one preferred embodiment, these third dimension surfaces consist onlyof virtual surfaces through which mass is permitted to pass. At leasttwo such sensing volumes may exist in close proximity to one another anddisposed in a streamwise direction from one another. In order to measureflow of a substance or material whose density varies with time, theamount of material would be measured in a first sensing volume and then,as the substance flows, that material would be measured subsequently ina second sensing volume. A cross correlation in time between the amountsof material in each of the volumes would indicate the flow velocity andmass divided by the cross-sectional area multiplied by the velocitywould be the mass flow rate.

This flow determining technique has been used in U.S. Pat. Nos.6,208,255 and 6,346,888. The sensors are placed sufficiently near oneanother that any variation of material density is minimized over thetime taken to traverse the distance between the two sensing volumes.

The sensors placed on the sensing volume measure the electrical capacityof the substance within the sensing volume. Knowing the dielectricconstant of the material (analyte) within the volume, a determination ofthe dielectric mass can be made, and thus an inference to the materialmass within the volume. Knowing the mass and volume, the density of thematerial is easily extracted. To calculate a mass flow rate, all that isrequired is a velocity.

A particular challenge is that of determining the mass flow rate of asaturated liquid-vapor mixture. A saturated liquid-vapor mixture isdefined as a mixture in which liquid and vapor are in equilibrium withone another. The cases of pure saturated liquid alone and pure saturatedvapor alone are included in this definition.

The subjects of equilibrium and saturated liquid-vapor mixtures arecovered in undergraduate thermodynamics courses, and are included in anytextbook used for such a course. An example text is “Fundamentals ofEngineering Thermodynamics,” Moran and Shapiro, Wiley, 7^(th) edition,2011, which is herein incorporated in its entirety by reference.

In particular, the quality of a saturated mixture is defined as:

$x = \frac{m_{g}}{m_{g} + m_{f}}$

where m_(f) is the mass of the liquid in the mixture and m_(g) is themass of the vapor in the mixture. Hence, m_(g)+m_(f) is the total massof the mixture. The density, ρ, of a saturated mixture is related to thequality as follows:

$\rho = \frac{\rho_{g}\rho_{f}}{{\left( {1 - x} \right)\rho_{g}} + {x\; \rho_{f}}}$

where ρ_(f) is the saturated liquid density and ρ_(g) is the saturatedvapor density. The mass of a substance with a density, ρ, within avolume,

, is:

m=ρ

irrespective if the substance is solid, liquid, vapor, or anycombination of these.

Saturated substances, such as anhydrous ammonia as applied toagricultural fields, may experience a change in quality, and hence,dielectric constant (permittivity) as they flow inside their respectiveconduits. Using the mass or density results from a single measurementvolume, outlined above, and using another technique to measure velocityor a value related to velocity provides mass flow rate.

For materials like anhydrous ammonia (or mixtures of anhydrous ammoniaand water or other materials) mass flow rate depends on the temperatureor pressure of the fluid such that similar masses would exist in avolume as a saturated liquid-vapor mixture depending on internaltemperature or internal pressure. The measurement of mass would thendepend on the knowledge of the dielectric constant of each phase and thevolume of each phase.

In the art, measurements using techniques other than capacity(permittivity) measurement for materials like anhydrous ammonia, thematerial is converted to a single phase, for example, by cooling, andthen the material flow rate is measured. In applications such as ananhydrous ammonia applicator for crop (field) injection, one concern isuniformity of application between various rows formed by individualinjectors. In that application, monitoring and/or controlling parameterssuch as pressure and/or temperature enhance the uniformity ofmeasurement results.

For example, in one preferred embodiment, a manifold with a single inputin which flow rate is measured using a two sensing volume technique oran alternate technique, and a multiplicity of outputs for which thequality of the substance varies and in which similar pressures andtemperatures exist allows uniformity of flow between the multiplicity ofoutputs to be monitored. In an agricultural application, uniformity ofanhydrous ammonia is a primary concern. Excess amounts of nitrogen (onesource is anhydrous ammonia) do not increase crop production butcontribute to run-off.

In the discussions to follow, time-delay is meant to be the time-delaybetween an input signal to the measurement path and the output signalfrom the measurement path. Since the system is causal, the time-delay ispositive, however, differential time-delay, being the derivative ofradian phase shift with respect to radian frequency, might be negative.

$t_{d} = {{- \frac{\theta}{\omega}} = {{- \frac{1}{360}}\frac{\varphi}{f}}}$$\tau_{d} = {{- \frac{d\; \theta}{d\; \omega}} = {{- \frac{1}{360}}\frac{d\; \varphi}{d\; f}}}$

Here θ is the radian phase shift of the output signal with respect tothe input signal, ϕ is the phase shift in degrees, co is the measurementradian frequency (in rad/s), f is the frequency (in Hz), t_(d) is thetime-delay, and τ_(d) is the differential time-delay. Either of thesetime-delays may be correlated to a dielectric constant which can be usedto infer material density.

In one embodiment of the present invention, electrical capacitymeasurement is used to infer density and another form of sensor yieldsvelocity or volumetric flow rate. In another embodiment of thisinvention, two electrical capacity sensor volumes are used, spaced aknown distance apart to determine velocity.

The mass flow rate, in, of a substance is related to the density, ρ, andvelocity, V, or the volumetric flow rate,

, as follows:

{dot over (m)}=ρ V A=ρ

where A is the cross sectional area of the volume perpendicular to theflow direction.

In still another embodiment, discrete particles are sensed as they passand may be time stamped for, for instance, grain planting equipment.

A further embodiment of the present invention provides for locating aparticle's path, said particle being, for instance, a single seed orgrain or a bubble within a liquid. In this case, the two electricalconducting plates are tapered. Hence, the distance the particle travelsbetween the plates at one side of the volume is greater than thedistance at the other side of the volume. The signature of theparticle's passing on one side of the volume is detectibly differentthan the signature when the particle passes on the other side of thevolume.

In a further embodiment a flow sensor apparatus is provided formonitoring a directed stream from an application port, the directedstream having a target directed portion and an off-target portion. Theflow sensor apparatus includes: a) a first electrically conductiveplate; b) a second electrically conductive plate disposed a distanceaway from the first electrically conductive plate; c) a firstelectrically nonconductive surface disposed to connect edges of thefirst and second electrically conductive plates; d) a secondelectrically nonconductive surface disposed to form a volume, the volumebounded by surfaces including the first electrically conductive plate,the second electrically conductive plate, the first electricallynonconductive surface, and the second electrically non-conductivesurface; e) a signal conditioning circuitry, having an input and anoutput, with the first and second electrically conductive plates; f)means for measuring the time-delay from the input to the output of thesignal conditioning circuit; g) means for correlating the measuredcircuit time-delay to the electrical capacity between the twoelectrically conductive plates; h) dielectric constant determiningcircuitry to determine an effective dielectric constant between thefirst and second electrically conductive plates; and, i) a computationalfunction to correlate the effective dielectric constant to a presence ofmaterial inside the volume. The first electrically conductive plate, thesecond electrically conductive plate, the first electricallynonconductive surface, and the second electrically nonconductive surfaceare positioned external to the application port.

In another aspect the present invention is embodied as an agriculturalproduct application system. In such an embodiment movable applicationequipment is provided including a flow sensor apparatus for monitoring adirected stream from an application port. The directed stream has atarget directed portion and an off-target portion. At least one upwindmoisture/humidity sensor is positioned upwind of the movable applicationequipment. At least one downwind moisture/humidity sensor is positioneddownwind of the movable application equipment. In another embodimentsensors may be utilized which are responsive to the refractive indexvariation of specific chemicals.

The novel features which are believed to be characteristic of thisinvention, both as to its organization and method of operation togetherwith further objectives and advantages thereto, will be betterunderstood from the following description considered in connection withthe accompanying drawings in which a presently preferred embodiment ofthe invention is illustrated by way of example. It is to be expresslyunderstood however, that the drawings are for the purpose ofillustration and description only and not intended as a definition ofthe limits of the invention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a perspective view of a capacity sensing volume of the presentinvention;

FIG. 2 is a perspective view of an anhydrous ammonia applicator for rowcrops;

FIG. 3 is a circuit diagram of a first preferred embodiment of thepresent invention;

FIG. 4 is a first plot of (ϕ,f) for two substances having unequaldieletric constants;

FIG. 5 is a circuit diagram of a second preferred embodiment of thepresent invention;

FIG. 6 is a second plot of (Of) for two substances having unequaldielectric constants;

FIG. 7a is a first schematic of a communication and computation flowdiagram;

FIG. 7b is a second schematic of a communication and computation flowdiagram;

FIG. 7c is a third schematic of a communication and computation flowdiagram;

FIG. 7d is a fourth schematic of a communication and computation flowdiagram;

FIG. 8a is a side elevation view of a first rotameter flow measurementdevice with electrical capacity sensing;

FIG. 8b is a side elevation view of a second rotameter flow measurementdevice with electrical capacity sensing;

FIG. 8c is a side elevation view of a third rotameter flow measurementdevice with electrical capacity sensing;

FIG. 9 is a side elevation view of a flow measurement device using apiston-spring assembly and electrical capacity sensing;

FIG. 10 is a side elevation view of a flow measurement device using apiston-spring assembly that plugs the exit in the absence of adequatepressure and uses electrical capacity sensing;

FIG. 11 is a depiction of two-phase flow;

FIG. 12 is a side elevation view of a single-volume detection system fordiscrete particles;

FIG. 13 is a side elevation view of a double-volume detection system fordiscrete particles;

FIG. 14 is a side elevation view of a grain planter;

FIG. 15 is a partially filled conduit containing flowing solidparticles;

FIG. 16 is a conduit carrying widely dispersed solid particles in afluid;

FIG. 17a is a trend line plot showing a first sensor response to adiscrete particle;

FIG. 17b is a trend line plot showing a second sensor response to adiscrete particle;

FIG. 17c is a trend line plot showing a first temporal derivative of thefirst sensor response to a discrete particle;

FIG. 17d is a trend line plot showing a first temporal derivative of thesecond sensor response to a discrete particle;

FIG. 18a is a plot of a first sensor response versus time;

FIG. 18b is a plot of a second sensor response versus time;

FIG. 18c is a plot of a cross-correlation of the first and second sensorresponses versus time increment;

FIG. 19 is a flow diagram illustrating comparing and warning functions;

FIG. 20 is a flow diagram illustrating a communication of a plurality ofsignals from a plurality of sensors;

FIG. 21 is a perspective and phantom view of a single-sensor volumeusing tapered electrodes;

FIG. 22 is a perspective and phantom view of a double-sensor systemusing tapered electrodes for two dimensional location sensing;

FIG. 23 is a perspective and phantom view of a double-sensor systemusing tapered electrodes, all at substantially the same longitudinallocation, for three dimensional location sensing;

FIG. 24 is a perspective and phantom view of a double-sensor systemusing tapered electrodes, electrodes for one sensor being upstream ofthe electrodes for the other sensor, for three dimensional locationsensing;

FIG. 25 is a first plot of sensor response versus time for a particlepassing through the double-sensor system of FIG. 22 or FIG. 24;

FIG. 26 is a second plot of sensor response versus time for a particlepassing through the double-sensor system of the present invention.

FIG. 27 is a perspective and phantom view of a single-sensor volumeusing arrays of electrodes;

FIG. 28 is a perspective and phantom view of a double-sensor systemusing one array of electrodes and one single electrode;

FIG. 29 is a perspective view of a first sensor system for detectingpermeability;

FIG. 30 is a perspective view of a second sensor system for detectingpermeability;

FIG. 31 is a perspective view of a first sensor system for detectingpermittivity and permeability;

FIG. 32 is a perspective view of a second sensor system for detectingpermittivity and permeability;

FIG. 33 is a circuit diagram of a sensor for detecting permeability; and

FIG. 34 is a plot of (Of) for two substances having unequal magneticfill in the sensor volume.

FIG. 35 is a perspective view, partially in cross-section, of anotherembodiment of the flow sensor apparatus which is detached from anapplication port of a planter row unit.

FIG. 36 is a perspective view of planter having a sprayer with a rearboom, and a detached flow sensor apparatus.

FIG. 37 is a schematic view of the sprayer boon with detached flowsensor apparatus and moisture sensors.

FIG. 38 is a schematic illustration of an agricultural productapplication system utilizing the detached flow sensors.

FIG. 39 is a perspective and phantom view of a detached double-sensorsystem using tapered electrodes for location sensing through the sensor.

DETAILED DESCRIPTION OF THE INVENTION

A sensor system volume 100 through which material may pass or in whichmaterial or matter is contained is shown in FIG. 1. Two sides 110comprise electrically conducting plates. Two more sides 120 compriseelectrical insulators. The capacity between the electrically conductingplates may be measured using methods commonly understood by those ofordinary skill in the art and explained in undergraduate electricalengineering texts. Circuits for this purpose are shown in FIGS. 3 and 5and their use described below. The arrows 130 indicate a flow direction,but the direction is immaterial. In fact, there may be no flow at all.An application of the present invention is the sensing of mass flow rateof anhydrous ammonia using an applicator 200, an example of which isshown in FIG. 2. Such an applicator is made to apply anhydrous ammoniato multiple rows, simultaneously.

An example equivalent circuit of the sensor of the present invention isshown in FIG. 3. An input alternating currents signal or summation ofvarious alternating current signals known as a Fourier series signal isincident on the left side of the circuit and an output signal would flowfrom the right side of the circuit. The frequency (frequencies) of thealternating current signal(s) may be from just above zero (directcurrent) to well into the optical region. Not shown is the input sourceor the terminating load. The input source and terminating load can be afairly simple source and a terminating resistor. At other times, thesource might consist of a power splitter allowing some of the power froma source to enter the circuit and other parts of the power to enter partof an amplitude-phase measuring circuit. The terminating circuit mightconsist of a transmission line, other components, and a subsequenttermination. The subsequent termination might be in the amplitude-phasemeasuring circuit.

Under the multitude of configurations, one purpose is to sense thetwo-port amplitude-phase response of the sensor volume. In manyapplications, the phase shift of the output signal versus the inputsignal will result in the desired characteristics being determined forthe sensor volume. In other situations, the input reflection coefficient(a measure of how much of the input signal is reflected from the inputport) can also be used to determine the characteristics of the volume.

The transmission and reflection parameters of the sensor volume might bedetermined by scattering parameter techniques, immittance matrixtechniques, chain matrix techniques, hybrid matrix techniques, etc.,known to those skilled in the art of circuit characterization. L1 and L2are input and output coupling inductors respectively, CA and CB areinput and output circuit matching capacitors, and C1, C12, and C2 arecapacitances associated with the sensor volume. In one embodiment, C12would represent the parallel plate capacity between an input electrodeand an output electrode, such as the plates 110 of FIG. 1.

The circuit in FIG. 3 can be represented in the art as a two pole filterwherein C12 is the coupling capacitor between two resonators. The phaseshift, at a given frequency, response of this circuit depends on thevalue of C12. The resonant frequency (for instance the passband centerfrequency) of the circuit depends on the value of C12. Increasing C12will lower the resonant frequency of the circuit.

Time-delay at a given frequency is related to phase shift through thecircuit by:

$t_{d} = {{- \frac{\theta}{\omega}} = {{- \frac{1}{360}}\frac{\varphi}{f}}}$

where t_(d) is the time-delay through the circuit, θ is the phase shiftthrough the circuit, and ω is the measurement frequency used.

A typical curve of phase shift versus frequency for the circuit is shownin FIG. 4 where the left most curve results from a C12 larger than thatfor the right most curve. At 40.68 MHz (an ISM frequency), this sensorshows a variation of, nominally, a negative 60 degree phase shift tonegative one-hundred twenty degrees phase shift. This results in achange in time-delay due to a change in phase shift at the samefrequency.

In one embodiment of the sensor, the time-delay can be measured with theuse of a phase frequency detector using two D flip-flops and one “and”function as is well known to those versed in the art. This time-delay isa function of the dielectric fill in the volume of the sensor 100.

For those applications wherein the analyte is a continuum (solid,liquid, vapor, or gas) the time-delay is a function of the permittivityof the material. For other applications where only the variation betweena plurality of sensors is to be indicated or measured, the uniformity oftime-delay between various sensors is the desired item.

In a preferred embodiment, the time-delay of the signal is less than theperiod of one cycle of the signal. As indicated below, in certainembodiments of the sensor, the time-delay might be longer than oneperiod of the signal. Differential time-delay measurements in that casewould allow the variation of dielectric fill to be measured.

In those configurations where the time-delay is less than the period ofone cycle, and since by causality the time-delay though the second pathis positive, a simple “exclusive-or” circuit can be used to measuretime-delay of the signal as is well known in the art.

Another embodiment of a sensor volume system would use the equivalentcircuit of FIG. 5 with a similar output phase shift versus frequency.The added resistors, R1 and R2 are included to represent loss in thecomponents. Core loss in an inductor manifests itself in an equivalentcircuit of an inductor as a resistor in parallel.

The variation in C12 used in the plot of FIG. 6 is different from thatused in the first plot shown above. However the phase shift versus C12can be calibrated to indicate the amount of change in C12 and thus thepresence of different dielectric materials in the sensor volume. Thevalue of C12 may be correlated to the nature of the material in thevolume.

Various applications may dictate the bandwidth of the sensor, the numberof frequency components of the signal of the input source, thesensitivity desired (phase shift versus capacity variation of C12) etc.Various applications might well indicate using alternate frequenciesother than 40.68 MHz and still other applications might use more thanone measuring frequency, either simultaneously or sequentially.

Other variations are anticipated in application to measuring thepermittivity of a volume. In some applications, phase shift might bemore easily measureable rather than time-delay. In still otherapplications, amplitude response of the circuit might be more easilyused to indicate volume permittivity. Phase shift and amplitude responseare related as well known to those versed in the art. Other sensorcircuit configurations could also be used.

As is known in the art, in various applications, the measurement of theimpedance (alternately the return loss) at one terminal of the circuitor using only one terminal (rather than two as shown) can often be usedto quantify the value of C12 or when the terminal intersection of C2 andC12 is at ground potential, the value of an equivalent C12.

Other embodiments include those for which signal phase can be quantifiedand measured. Time-delay, by causality, through the circuits would bepositive. However, differential time-delay, which can also be measured,might be negative in some regions of the frequency domain. In apreferred embodiment, as shown in the two circuits above, it istime-delay that is measured. The time-delay through the circuit, forinstance, using a long transmission line in a return path may make thetime-delay longer than one cycle of the signal. The time-delay measuredby measuring zero crossings would then be in error by an integermultiple of a period. However, differential time- delay would still givean indication of a change in the time-delay within the measurement cell.

The application of the art discussed here can provide for row to rowsensing of anhydrous ammonia or for row to row sensing of other sprayerapplications.

Mass flow rate for more complex systems can be determined and is auseful application using the techniques described here. However, inorder to simplify and lower the cost of a system for anhydrous ammonia,mass only can be measured for many applications. Ammonia tool bars havea distribution manifold. These manifolds have an input port and severaloutput ports. Mounting a mass flow rate sensor on each output port willmonitor the mass flow rate to each row.

Planter monitoring systems are provided land speed information andexpect a pulsed signal indicating seed counts from the planter units.The sensor system, in some embodiments of the present invention, whenemployed to measure mass flow rate, will put out a number or frequencyof pulses as a function of the mass flow rate. On the ammonia functionthe monitor will sense the mass—usually pounds—per acre. When monitoringplanting equipment and the flow rate of seeds, the seed monitoringfunction uses a bar graph function to compare different seed rates foreach sensor and sets an alarm if the sensor signals do not conform tothe allowable tolerance. Adjusting the flow rate for individual rows caneither be done manually by a valve system or electronically with anautomatic controller function. Such an automatic control function wouldemploy an automatic control algorithm, such as a Proportional, Integral,Differential (PID) algorithm. The seed function can be reprogrammed toread mass or seed flow rate rather than seeds per acre.

This same function can be used to monitor liquid systems and sprayersexcept the sensor will be used to determine velocity instead of, or inaddition to, mass. In a liquid system the density is substantiallyconstant and the speed of the flow will vary according to theapplication rate. The sensor will put out a number of pulses accordingto the flow velocity.

In one embodiment of the present invention the flow sensing system isaugmented in various applications with prior art rotameter flow sensors800 shown in FIGS. 8a-8c or the like using a truncated cone 810, bead820, cone, or other shape having a known drag coefficient versus flowrate function. These additional sensors may be mounted vertically to usegravity as the force to position the sensor element, or buoyancy fordownward flow, as shown in FIG. 8 c, or may use spring force to positionthe sensor element 910 (FIG. 9), 1010 (FIG. 10) for applications whereimpulse or vibration are non-negligible, or when the installation isnecessarily non-vertical.

When microwave frequencies are employed with the present sensor 710 asapplied to a rotameter 800 or similar flow meter, when using the propermaterial, the sensor 710 will respond to the total mass in the sensorvolume 100. Since liquids such as ammonia and water have a higherdieclectric constant than their respective vapors or air, if vapors arepresent in the meters 800, the physical movement of the sensor element810, 820 will correspond to the total volume of the flow. So unlike thestandard rotameter 800 false measurement caused by non-liquid flow areeliminated.

Flows of fluids such as ammonia, which can be 90% vapor 1120 and 10%liquid 1110 (see FIG. 11) by volume, a much more accurate flow readingmay be obtained without cooling.

The flow sensor 900 shown in FIG. 9 makes use of a piston 910 with anorifice 920 providing flow resistance and a consequent streamwiseforce—against the spring force.

The flow sensor 1000 of FIG. 10 makes use of a positive-sealing piston1010 with a conical plug 1020 and a pressure relief line 1030 toequalize the pressure between the space above the piston 1010 and theflow exit 1040.

The electric capacity sensor 710 of the present invention can be usedwith these additional sensor elements 800, 900, 1000. The material usedin the bead 820, cone 810, piston 910, plug 1010, or other movablecomponent is chosen so the dielectric constant of mass is different fromthat of the fluid being measured. When the bead 820 or sensing element810, 910, 1010 is moved by the flow, the resulting position change isdetected by the sensor system 710 as described. The location of thesensing element 810, 820, 910, 1010 is a function of the flow rate andis sensed by the increment change in location of the sensing element810, 820, 910, 1010 material in the measurement volume. The knownfunction of bead or cone location to flow rate is used to calculate theflow rate. This known function is determined by the manufacturer or fromempirical data.

In addition to the system augmentation in the sensor area, the systeminterface to other systems and/or vehicles is augmentable with the useof computational machinery as depicted in FIG. 7a -7 d. A monitor andoperator interface, such as a seed monitor 1410 (FIG. 14) is likelymounted in the space occupied by the operator, such as an agriculturaltractor.

The sensor 710 is responsive to various analytes—liquid, solid,particulate FIGS. 12, 13, 15, and 16, liquid/vapor mixtures FIG. 11,etc. The computational machinery of FIGS. 7a-7d can process the varioussignals from different analytes to give a signal indicative of thethermodynamic properties of the material. The computational functionsmay be performed by one or more of a computer 730, a microcomputer 740,a microcontroller 750, or a microprocessor 760. For example, the signalfrom a mixture of liquid 1110 and vapor 1120—see FIG. 11—might beaugmented by an input from another sensor, tractor, or implement toaccount for the characteristics of a particular environment ormeasurement condition. The signal can be processed to conform to variouscommunication bus 720 architectures for transmission of information. Theinformation may be unilateral or bilateral and might contain controlinformation or commands in addition to signaling information. Referringnow to FIGS. 11, 15, and 16, for flow rate determinations of a materialor substance flowing as a continuum, the response from Sensor A may looklike the noisy signal shown in FIG. 18 a, whereas the response fromSensor B may look like the noisy signal shown in FIG. 18 b. Using asampling technique and a correlation technique, a signal similar to thatindicated FIG. 18 c results. The value of At at the peak “G” of thissignal is the time required for the material to travel between the twomeasuring volumes. For high flow rates in which a greater volume ofmaterial passes per unit of time, the time difference is less, whereasfor lower flow rates, in which a lesser volume of material passes perunit of time, the time difference is greater. In very low flow rates orno flow rate, there would be no discernible signal peak.

The signals shown in FIGS. 18a and 18b may be received by an operatorinterface, such as a seed sensor unit 1410. The sampling and correlationmay also be carried out in the seed sensor unit 1410, and the pertinentinformation displayed thereon for the operator. However, the signals ofFIGS. 18a and 18b may also be received by any of the computer 730,microcomputer 740, microcontroller 750, or microprocessor 760, and thecalculations carried out therein. The results of these calculations maythen be sent, via the communication bus 720 to the operator interfaceunit 1410 for display, alarms, etc. In the latter case, the results ofthe signal processing must be provided to the operator interface unit1410 in a form compatible therewith. As those of ordinary skillunderstand, a seed monitor 1410 provides the operator with informationabout the performance of the planter and planting operation, such aswhether the operation is within tolerance. The same kind of informationand alarming would be provided by the operator interface unit 1410 whendevoted to anhydrous ammonia application.

Additionally, the sensor system 710 of the present invention may be usedin the flow conditions of FIGS. 11, 15, and 16 to sense materialdensity. Given the density, time-delay, and the volume of themeasurement volume 100, a mass flow rate may be calculated.

In FIGS. 12 and 13, an instance of a discrete particle 1210 is shown. Anexample of this is the planter 1400 of FIG. 14, where grain, such ascorn 1210 drops through a conduit 1420. In the embodiment illustrated inFIG. 12, the passage of a particle 1210 is sensed by the sensing system710 as a change in capacity as shown in FIG. 17 a. The signal may bedifferentiated with respect to time—the first temporal derivative—toobtain a signal such as that shown in FIG. 17 c, and the zero-crossing“C” detected to pinpoint the time at which the particle 1210 passed.This time may be compared to the time at which the next (or previous)particle passed to gage the operation of the planter 1400.

The signals shown in FIGS. 17a and 17b may be received by a seed sensorunit 1410, as are commonly used to monitor planter performance. Thetemporal derivatives may also be calculated in the seed sensor unit1410, and the pertinent information displayed thereon. However, thesignals of FIGS. 17a and 17b may also be received by any of the computer730, microcomputer 740, microcontroller 750, or microprocessor 760, andthe calculations carried out therein. The results of these calculationsmay then be sent to the seed sensor unit 1410 for display, alarms, etc.

The embodiment illustrated in FIG. 13, two sensor systems, A and B, 710are disposed in the flow direction from one another, with sensor systemA being upstream of sensor system B. In this case, the signals shown inFIGS. 17a and 17b for sensor system A and B, respectively are sensed. Inthis embodiment, the signals from both sensors may be differentiatedwith respect to time to produce the signals in FIGS. 17c and 17 d.Again, the time of the zero crossing “C” and “D” for each signal isdetected. In this case, the two times of zero crossing are subtracted,indicating the time taken to traverse the distance between the twosensor systems, A and B, 710, thus providing a velocity value.

FIG. 19 illustrates the communication bus 720 communicating with theoperator interface 1410. Within the operator interface, the signal iscompared to at least one tolerance value in a comparator function 1910.The tolerance value may be a low or high threshold, or both. If thesignal does not satisfy the tolerance or tolerances, a warning signal isprovided to the operator in a warning function 1920.

In FIG. 20, a plurality of sensors 710, are in communication with acomputation function 2010 where the signals are processed in anappropriate manner, such as shown in FIGS. 17a-17d or FIGS. 18a -18 c.The result is sent, via the communication bus 720 to the operatorinterface 1410, where the results are displayed, compared, and otherwisemade available to the operator in a fashion easily understood. Theplurality of signals received from the plurality of sensors 710 may becompared with one another in the comparator function 1910 to determineif the application is substantially even across rows.

The computation function 2010 may, for instance, provide a signalentirely compatible with a seed monitoring system 1410, as used duringplanting. The seed monitor 1410 may then make comparisons as shown inFIG. 19 exactly the way it carries this function out for the plantingoperation. Further, the tolerance may be adjusted to satisfy theoperator and the needs of the operation.

In many instances, it is important to know not only the presence andsize of a particle 1210 being sensed but the path that particle 1210follows in a tube. For the purposes of this document, including theclaims, a particle 1210 is defined as a single solid particle 1210, suchas a seed, or a bubble within a liquid. For instance, in a seed plantingoperation, it is desirable to know that the seed 1210 does not deflectfrom the tube sides and that its position on exiting the tube can bemonitored so its position on planting can be controlled—especially forhigh planter velocities.

The signal derived from sensing the particle's 1210 position can be usedin a feedback control system to control a particle 1210 releasemechanism designed to control the particle's path within the volume 100.

Particulate position may be monitored using the electrical capacitybetween two tapered plates 2100 such as shown in FIG. 21. It should benoted that the electrical capacity may not be directly measured, but thepermittivity of the material filling the sensing volume will change theelectrical capacity between the electrodes. This capacity change willchange the sensing circuit's response and indirectly the inferredcapacity—and thus permittivity—is measured. In a similar manner, if theelectrodes were changed to a current loop, magnetic properties in thesensing volume can be measured in a similar manner. Thus, thisembodiment involves tapering the two electrically conductive plates in atransverse direction to matter flow; and sensing a transverse locationof the matter between the two tapered electrically conductive plates.

The position sensing system of FIG. 21 may be expanded upon to locateparticles in all three dimensions by adding a second sensor on adjacentwalls of the volume as shown in FIGS. 23 and 24. Considering theorientation of the volumes of FIGS. 23 and 24, the two tapered plates2100 indicate location in a horizontal plane while the two taperedplates 2300 indicate location in a vertical plane. It is well understoodby those of ordinary skill in this art that the embodiments illustratedin FIGS. 23 and 24 may be disposed in any orientation desired, and arenot limited to determining horizontal and vertical positions.

In FIG. 24, the two tapered plates 2100 are shown upstream of the twotapered plates 2300. This arrangement helps avoid electric fieldinterference from the two sensors and may be advantageous in determiningparticle speed.

The responses from two such sensors 710, as shown in FIG. 22, in theflow path further help to ensure the particles 1210 follow a pathwithout deflecting from the volume's 100 walls. There are pathsparticles 1210 may follow having deflections—path A—that provide thesame position response signal as a particle flowing without deflections2110, 2120, 2130, 2140. However, the time between sensor responsesdiffers between that for a direct path 2110, 2120, 2130, 2140 and a pathwith deflections—path A. A diagonal path A, resulting from a deflection,exhibits a longer path than a direct path 2110, 2120, 2130, 2140 or adiagonal path without deflections—path B—between two sensor volumes 100and thus a difference in sensed time of travel.

Path B, FIG. 22, shows a path through two sensor electrode volumes 100that passes at different lateral positions of the two volumes 100 andwould be detected as different. FIG. 25 shows three different possibleexample responses. Note that the top trend 2530, representing a responsefor path 2130 has two equal amplitude and equal pulse-width responsesspaced a time, At, apart. Path 2130 goes directly through the tube,parallel to the longitudinal direction.

Compare the response 2530 to the response for path A, shown as thebottom response 2500A in FIG. 25. Path A includes a deflection 2210 inthe path of the particle 1210. There are also two equal amplitude andpulse width, WA, responses shown in trend 2500A except that these pulseresponses are farther apart in time than those in response 2530.Predetermined time-delay data stored in the computational function 730,740, 750, 760, entered manually or computationally determined, permitsthe system to identify this path as a path with a deflection.

The response for path B, shown as the middle trend 2500B in FIG. 25, hastwo different width responses, w_(B1), w_(B2), because the particle 1210passes between the sensing electrodes 2100 of the respective sensors 710at positions where the sensing electrodes 2100 are of a different width.Also note that the time-delay between the pulses is somewhat longer thanthe direct path time-delay of response 2530.

Referring now to FIG. 26, the time a particle 1210 takes to pass avirtual plane placed across its path until it approaches the edge of thetapered sensor varies depending on which path within the tube it takes.

The time relationship for the different normalized responses of a singleelectrode volume 100 shown in the left side of FIG. 26 would result ifone plotted the signal response starting at time equals zero when aparticle 1210 passes a virtual plane within the tube. The signal thenbegins to rise as the particle 1210 approaches the edge of the taperedelectrode volume 100 and, for different paths, the rise time variessince the distance from the virtual plane to the tapered edge of theelectrode varies depending on the particle's 1210 path, i.e., whatlateral position the particle 1210 passes between the electrode pair.

However, it is not known a priori when the particle 1210 is approachingthe sensor 710. The important parameter of the response is the timedifference, Δt₁, Δt₂, Δt₃, Δt₄, between the time when a particle 1210approaches the sensor electrode 2100 volume 100 and the time when theparticle 1210 leaves the sensor electrode 2100 volume 100 as shown byplotting the responses as seen on the right side of FIG. 26.

Some acceleration of the particle 1210 over the distance traveled withinthe sensor 710 electrode volume 100 is possible, but with sensordimensions adequately small with respect to velocity multiplied by timein the sensor volume 100, the differences in velocity may be neglected.In addition, with historical data determined computationally by a systemor having been manually inputted, the expected time-delays versus pathwould be nominally known. For instance, when a particle 1210 undergoesgravitational acceleration, the expected velocity (and thus time knowingthe distances) would be nominally known. However, the nominal velocitycan also be quantified by knowing the time response between twodifferent sensor 2100 volumes 100 within the flow path.

In applications in which the mechanical design is such that thelikelihood of particle 1210 deflection—from conduit walls, forexample—is small, it is possible a single tapered electrode 2100 sensor710 may be adequate to indicate the lateral position of the particle1210.

By way of explanation, in FIGS. 21 and 22, dashed lines are shownbetween the sensor electrodes to visually clarify where the flow pathsare for the responses shown in FIG. 26 as well as where a particle 1210is disposed, vertically, in the tube. The paths 2110, 2120, 2130, 2140shown in FIG. 21 are shown entering a virtual cross-section of the flowtube, progressing through a virtual cross-section between the sensorelectrodes 2100 and then exiting the volume 100 via an exit virtualcross-section. Four different flow paths 2110, 2120, 2130, 2140 areshown but there is a multitude of flow paths for a particle 1210 tofollow anywhere across the virtual cross-sections, including paths thatare at an angle, i.e. not parallel to the longitudinal direction. Sensor710 responses for particles 1210 will nominally have the same amplitudeirrespective on their vertical—as shown in the figures—position at thetime of passage.

FIG. 27 shows a representation of the sensor electrode volume 100including of two arrays of electrodes 2700. In a similar embodiment,shown in FIG. 28, one of the arrays of electrodes 2700 is replaced by asingle electrode 2800 encompassing one of the surfaces. The distancebetween the individual components of the electrode array 2700 arenecessarily small with respect to the array dimensions. If all of theelectrodes within an array 2700 on a single side communicateelectrically with one another, electrically their summed responses aresubstantially the same as the response from a single electrode 2800covering the same area. This is a result of the fringing electricalfield existing on the edges of individual electrodes composing anelectrode array, or part of an electrode array. Hence, the individualelectrodes appear larger than their physical dimensions.

Summing responses from different groups of the arrayed electrodes canmake the summed responses appear to simulate a tapered or stepped sensorelectrode volume. Summing the responses from a group of electrodes orsensing responses from individual electrodes will thus indicate where,in the volume, a particle 1210 passes.

The time-delay of the responses from electrodes on the entering side andthe exiting side indicates average velocity as well. With thecomputational power available from current computer processors ofvarious forms 730, 740, 750, 760, these measurements and computationscan be accomplished with relative ease. The arrayed electrodearrangement is slightly more complex and costly than that of anon-arrayed electrode.

The frequency or frequencies of an alternating current source chosen forthe measurement—and thus the signal generator frequency orfrequencies—depend on several factors. In order to get a reasonablevalue of transfer admittance across the measurement volume, thefrequency should be sufficiently high that the impedance of the capacitybetween a set of input and output electrodes 2100 is close to the sameorder of magnitude as the impedance level chosen for the sensor's 710circuitry. In many cases, the sensor's 710 detection circuit works atnominally 50 ohms but can be some other value of impedance as well.

Further, the frequency is chosen sufficiently low that the crosssectional areas of the input and output for particle 1210 or fluid flowis small enough that the waveguide formed by the housing (forming anelectromagnetic waveguide) does not permit the electromagnetic energy toescape over the input and output areas.

These and other microwave circuit design considerations will often beinvolved in the choices of frequency and dimensions of the circuit anddescribed in the book, Introduction to Microwave Circuits, RadioFrequency and Design Applications, by Robert J. Weber, IEEE Press, ISBN0-7803-4704-8, 2001, which is hereby incorporated in its entirety byreference.

Microwave effects might be determined by parasitics or distributedeffects associated with the sensor 710 circuit and its components or thechoice of measurement frequencies versus sensor 710 size.

The present invention is not limited to any range of frequencies.However, frequencies in the ranges of Radio Frequency (RF) andmicrowaves may be chosen and, indeed, advantageous. In otherapplications, optical frequencies may be advantageous.

As indicated above, the sensing electrodes can be changed to loops todirectly measure magnetic properties of materials such as magneticpermeability, effective magnetic permeability, etc., by measuringtransfer inductance values. In a sensor with two volumes, one volumecould measure permittivity values and another volume could measurepermeability values of the flow with one volume using capacitance platesand another volume using inductive loops.

When monitoring the transport of magnetic particles or magnetic fluids,e.g. ferrofluids or magnetorheological fluids, it is advantageous to usesensor volumes 100 comprising an inductive loop to sense the amountand/or presence of the material.

For instance, in mangetorheological fluids the ferroparticles may settleunder gravity or in a magnetic field. It is desirable to know whetherthis has transpired and/or the quantity of particles in the fluid. Thecounting of magnetic particles such as steel screws dropping or flowinginto queuing or shipping containers etc. could be accomplished with amagnetic sensor volume.

FIG. 29 shows a perspective view of a sensor volume 100 with sensingloops 2910 instead of sensing plates 2100, 2700. The sensing loops 2910may be multi-turn or a simple loop as shown. The sensing loops 2910generate magnetic fields in the sensor volume 100. Magnetic materialpassing through the volume will change the mutual impedance of thesensor volume 100 and thus the transmission of electromagnetic energythrough the sensor volume 100.

In FIG. 30, the sensor loops are shown as small plates 3010 instead ofloops. However these plates 3010 are electrically grounded on one endinstead of being free floating as in a capacitance measurement. The ballon the end of the loop 3010 is to indicate that the loop 3010 isgrounded to the surrounding conducting boundary.

The cross-hatched 2930 area indicates the conducting boundary surroundsa dielectric material that guides the magnetic particles or fluidsthrough the sensor volume 100. The surrounding conducting boundary andthe dielectric material that guides the particles or fluid may berectangular or circular in cross section, as well as having other crosssectional geometries. The present invention is not limited to aparticular shape cross section.

At times it may be advantageous to know the permittivity of the mediumcarrying the magnetic material. A sensor for detecting magneticpermeability and permittivity is shown in FIG. 31 where loops 2910 andcapacitive plates 3110 are disposed normal to one another. In FIG. 32,the loops 2910 and capacitive plates 3110 are disposed on the same wallssides of the sensor volume 100.

With flow in the direction of the arrows 2920, the relative positions ofthe loops 2910 and plates 3110 in FIGS. 31 and 32, imply the magneticproperties (permeability) are first measured and then the dielectricproperties (permittivity) are measured as the measured material istransported through the sensor volume 100. However, the plates 3110 andloops 2910 could be reversed in relative to the flow direction andmeasure the dielectric properties first and then the magnetic propertiesmeasured secondly.

With careful design, as is well known by those of ordinary skill in theart, the loops 2910 shown in FIG. 31 could be moved to be adjacent tothe capacitive plates 3110 and have the magnetic and dielectricproperties measured simultaneously. The present invention is not limitedto any particular measurement order.

FIG. 33 shows an equivalent circuit 3300 diagram of the sensor volume100.

Inductances, L1, L12, and L2 represent the sensor volume. Elements, C1,L3, and C3 represent components for matching the impedance of the sensorvolume 100 to the appropriate value. Likewise, elements, C4, L4, and C2represent components for matching the sensor volume 100 to theappropriate value. These values are such that, with a measurementalternating current source on the left and a load on the right, thecircuit response will give the amplitude and phase response of thecircuit as desired. In this case, L12 varies as a function of magneticmaterial fill in the sensor volume. Again, the circuit can be changedinto a two-pole filter configuration with L12 representing the couplingbetween an input resonator and an output resonator.

FIG. 34 shows a representative phase curve for varying magnetic fill(L12 varying). The time-delay can then be empirically or theoreticallyrelated to the amount of magnetic fill in the sensor volume 100. As isknown to those skilled in the art, measurements on the input port of theequivalent circuit 3300 may be used to indicate the value of L12 andthus magnetic fill in the sensor volume 100.

A typical curve of phase shift versus frequency for the circuit is shownin FIG. 34 where the left most curve results from a larger magnetic fillthan that for the right most curve. This sensor shows a variation of adegree phase shift due to the quantity of magnetic fill. This results ina change in time-delay due to a change in phase shift at the samefrequency.

Just as in the dielectric property case, the time-delay through themagnetic sensor volume 100 can be used to gauge the presence, and therelative amount of magnetic material in the sensor volume 100.

All the same applications and functionality shown in FIGS. 1, and 7 a-20pertains to the present inductive loop-type sensor volume 100 as well asthe capacitive plate-type sensor volume 100.

Referring now to FIG. 35, another embodiment of a flow sensor apparatus3510 is illustrated on a corn planter row unit, designated generally as3520. The flow sensor apparatus 3510 is positioned external to anapplication port 3522 of a supply tube, designated generally as 3524.The supply tube 3524 may be, for example, a liquid tube or granulartube. The detached flow sensor apparatus 3510 is mounted via a supportbracket 3526 attached to the planter frame of the row unit 3520. Thebracket may be attached to a side bolt or other part of the planterframe that the supply tube 3524 is attached to so that it is stationarywith respect to the supply tube 3524. Although this embodiment has beenillustrated relative to a corn planter row unit it may be used on othertypes of row units, or other application equipment.

Referring now to FIG. 36 another type of application equipment in whichthe attached flow sensor apparatus may be utilized, is illustrated. FIG.36 shows a self- propelled sprayer vehicle 3600 with a rear boom 3610.

FIG. 37 shows an enlarged portion of a sprayer boom 3610 with nozzles(which may alternatively be referred to as discharge ports orapplication ports) 3612. The nozzles 3612 are operatively positionedrelative to associated detached flow sensors 3614 that are configured tomeasure the volume of spray and pattern of the spray at a certainposition below the application ports (i.e. nozzles) 3612. Preferably,above the boom, detached moisture sensors 3616 are positioned thatmeasure the humidity (i.e. moisture content) of the air. Alternativemounting positions of the detached moisture sensors 3616 can be providedfor mounting on the cab or other locations on the self- propelled sprayvehicle 3600. Such alternate detached moisture sensors 3618 can be seenin FIG. 36. Suitable sprayer boom mounting brackets 3620 are utilized.

FIG. 38 is a schematic illustration of a field with indicated winddirections and sensors to determine movement of spray drift moving offthe target area. FIG. 38 illustrates how to position sensors to monitorspray drift that flows off the target area or field being treated.Sensor A (i.e. upwind moisture/humidity sensor) is positioned upwind.Moisture/humidity sensors B1, B2, etc. can be mounted on the sprayervehicle or the sprayer boom. The overall agricultural productapplication system, which may be the planter application or the sprayapplication, can include a downwind moisture/humidity sensor C. The flowof the spray to the non-target area can be measured by comparing thereadings of sensors A, B, and C. Depending on field conditions and windconditions, the number and position of sensors can be varied for moreaccurate measurement of flow. The various flow sensor apparatusdescribed above and below can be used in this agricultural productapplication system.

FIG. 39 is a perspective and phantom view of a detached sensor systemusing tapered electrodes 3910, 3912, 3914, 3916 for location sensingthrough the sensor. The tapered electrodes have a different responsewhich is used to determine the direction of material (i.e. contents)flowing through the sensor. If the material passes the wider part of thesource electrode 1 it produces a signal which is detected by thedetector electrode 1. As the material passes the narrower part of thesource electrode 2 it produces another signal that is detected bydetector electrode 2. Comparing the amplitude of the two signals theposition of the material in the sensor body can be determined, and thusthe path which the material takes through the sensor body. The sensorbody includes any physical housing, the electrodes, and suitablecircuitry which allows attachment of the detached sensor system to thevarious equipment. Thus, as in previous embodiments, this methodinvolves bounding a volume by surfaces comprising a first electricallyconductive plate, a second electrically conductive plate, not inphysical contact with the first electrically conductive plate, and atleast two sides made of electrically insulative material also boundingthe volume. The source electrodes, in one preferred embodiment, emit analternating-current. The detector electrodes and interface circuitry arereactive circuit elements. The material flowing through the sensorcreates a change in the reactance in the circuitry.

The pairs of electrodes facilitate determining the path that materialtakes through the volume between the pairs of electrodes. The response,amplitude or phase, of the sensing systems connected between the firstpair of electrodes (i.e. spaced-apart plates) 3910, 3912 and the secondpair of electrodes 3914, 3916 in conjunction with determining the timeof passage of material between the electrodes facilitates determiningwhether the material passes to one side, the middle, or the other sideof the volume. Assuming material passing into the front and out of therear of the sensor as depicted in FIG. 39, and when the path thematerial takes is to the left of the volume (i.e. Path 3), the sensingsystem response will be apparent for a longer period between the firstpair of electrodes 3910, 3912 than the sensing system response that isapparent from the second pair of electrodes 3914, 3916. When the paththe material takes is down the middle of the volume (i.e. Path 2), theresponses of the two sensing systems will be substantially equal in timeduration. In addition, if the amplitude responses of the sensing systemsfor each of the two pairs of electrodes are substantially equal, thesensing system amplitude response from the first pair of electrodesversus the sensing system amplitude response from the second pair ofelectrodes is indicative of the path taken by the material. When thepath is to the left, the sensing system's amplitude response for thefirst pair of electrode will be higher than the sensing system'samplitude response for the second pair of electrodes. When the materialtakes a path down the middle of the volume, the amplitude responses foreach pair of electrodes will be substantially equal. When the path is tothe right (i.e. Path 1), the sensing system's amplitude response for thefirst pair of electrode will be lower than the sensing system'samplitude response for the second pair of electrodes. When used in acomparison detection system, the absolute magnitude of response fromeach pair of electrodes is not needed to determine the position ofmaterial passage. By comparing the amplitude responses from the twosensing systems in a relative magnitude manner, the path the materialtakes can be determined.

Position source electrodes and detector electrodes 3910, 3912, 3914,3916 such as shown in FIG. 39 and specific for planter tubeapplications, in one preferred sensor embodiment has a width ofapproximately 1.5 inches and a height of ⅝ inches. In one preferredembodiment, they are placed such that seeds or granules travel passthrough the volumes over which the tapered electrodes are nominally 1.75inches center line to center line distance apart in the direction oftravel. Position sensors for typical liquid based applicators may be ofa larger size and of a different aspect ratio. The maximum size islimited such that at the frequency used for the sensing systems, theelectromagnetic fields established in the sensor volume remainevanescent and not propagating external to the sensor as is well knownto those skilled in the art.

Refractive index is the square root of relative dielectric constant.Incorporating sensors responsive to refractive index variation ofspecific chemical species into the apparatus of sensors 3614 facilitatestracking and placement determination of specific chemicals such asherbicides, insecticides, etc. In one preferred embodiment, a miniaturesensor such as described in “Patterning of nanophotonic structures atoptical fiber tip for refractive index sensing,” Shawana Tabassum, YifeiWang, Jikang Qu, Qiugu Wang, Seval Oren, Robert J. Weber, Meng Lu,Ratnesh Kumar, Liang Dong, SENSORS 2016, Caribe Royale All-Suite Hoteland Convention Center, Orlando, Fla., October 30-November 2, 2016, canbe easily incorporated into the volume of sensors 3614. A multiplicityof such sensors facilitate determining not only amounts of chemicalspassing through the volume but their position of application byjudicially placing such sensors in the sensor 3614.

In some embodiments additional computation operations and resultantwarning(s) may be utilized when the output of individual sensors of themultiplicity of sensors vary indicating no flow or limited flow whenflow or full flow should be present.

The above embodiments are the preferred embodiments, but this inventionis not limited thereto. It is, therefore, apparent that manymodifications and variations of the present invention are possible inlight of the above teachings. It is, therefore, to be understood thatwithin the scope of the appended claims, the invention may be practicedotherwise than as specifically described.

What is claimed is:
 1. A method of sensing a presence of a material, themethod comprising: (a) disposing two electrically conductive plates apredetermined distance apart; (b) incorporating a signal conditioningcircuit, having an input and an output, with the two electricallyconductive plates; (c) allowing matter to be present between said twoelectrically conductive plates; (d) measuring a time-delay with thematter from the input to the output of the signal conditioning circuit;(e) correlating the measured circuit time-delay to an electricalcapacity between the two electrically conductive plates; and (f)correlating a measured electrical capacity to the presence and amount ofthe matter between said spaced-apart plates, wherein said matter isdirected to be present between said two electrically conductive platesby an application port, said two electrically conductive platespositioned external to said application port.
 2. The method of claim 1wherein measuring the electrical capacity comprises sensing a change inthe electrical capacity.
 3. The method of claim 1 wherein measuring theelectrical capacity comprises sensing a signal related to an effectivedielectric constant of a mass in the volume.
 4. The method of claim 3additionally comprising: (a) taking a first temporal derivative of thesignal related to the effective dielectric constant of mass; (b)determining a zero-crossing of the first temporal derivative; and (c)calculating a time at which the zero-crossing occurs.
 5. The method ofclaim 1 wherein correlating the electrical capacity measurement to thepresence of the matter comprises empirically determining a correlationbetween a thermodynamic state of the material and the electricalcapacity of the material.
 6. The method of claim 1 wherein correlatingthe electrical capacity measurement to the presence of the mattercomprises correlating a dielectric mass to a mass of the matter.
 7. Themethod of claim 1 wherein a volume is bounded on two sides by the twoelectrically conducting plates and the matter is stationary relative tothe volume.
 8. The method of claim 1 wherein a volume is bounded on twosides by the two electrically conducting plates and the matter is movingrelative to the volume.
 9. The method of claim 1 wherein the matterbetween said spaced-apart plates comprises a sensing element and thepresence of the matter comprises a location of the material.
 10. Themethod of claim 9 wherein the sensing element comprises a shape selectedfrom the group consisting of a bead, a cone, and a truncated cone. 11.The method of claim 9 wherein the location the sensing element changesas a function of flow rate.
 12. The method of claim 9 wherein adielectric constant of the sensing element is not equal to a dielectricconstant of a flowing substance between the spaced- apart plates. 13.The method of claim 1 additionally comprising: (a) tapering the twoelectrically conductive plates in a transverse direction to matter flow;and (b) sensing a transverse location of the matter between the twotapered electrically conductive plates.
 14. The method of claim 13wherein sensing a transverse location comprises: (a) sensing a durationof a signal of the electrical capacity; and (b) correlating saidduration to the transverse location of the matter between the twotapered electrically conductive plates.
 15. The method of claim 13wherein the two tapered electrically conductive plates comprise a firsttwo tapered electrically conductive plates and the transverse locationcomprises a first-plane transverse location, that is, the transverselocation in a first plane, the method further comprising: (a) tapering asecond two electrically conductive plates in a transverse direction; (b)disposing the second two electrically conductive plates at an angle, notparallel, to the first electrically conductive plates; and (c) sensing asecond-plane transverse location of the matter between the second twotapered electrically conductive plates.
 16. A flow sensor apparatus formonitoring a directed stream from an application port, said directedstream having a target directed portion and an off-target portion, saidflow sensor apparatus comprising: (a) a first electrically conductiveplate; (b) a second electrically conductive plate disposed a distanceaway from the first electrically conductive plate; (c) a firstelectrically nonconductive surface disposed to connect edges of thefirst and second electrically conductive plates; (d) a secondelectrically nonconductive surface disposed to form a volume, saidvolume bounded by surfaces comprising the first electrically conductiveplate, the second electrically conductive plate, the first electricallynonconductive surface, and the second electrically non-conductivesurface; (e) a signal conditioning circuit, having an input and anoutput, with the first and second electrically conductive plates; (f)means for measuring the circuit time-delay from the input to the outputof the signal conditioning circuit; (g) means for correlating themeasured circuit time-delay to the electrical capacity between the twoelectrically conductive plates; (h) a dielectric constant determiningcircuit to determine an effective dielectric constant between the firstand second electrically conductive plates; and (i) a computationalfunction to correlate the effective dielectric constant to a presence ofmaterial inside the volume, wherein said first electrically conductiveplate, said second electrically conductive plate, said firstelectrically nonconductive surface, and said second electricallynonconductive surface are positioned external to said application port.17. An apparatus, comprising: (a) a first inductive loop; (b) a secondinductive loop disposed a distance away from the first inductive loop;(c) a signal conditioning circuit, having an input and an output,incorporated with the first and second inductive loops; (d) means formeasuring a time-delay from the input to the output of the signalconditioning circuit; (e) means for correlating the measured circuittime-delay to the effective magnetic permeability of matter between thefirst and second inductive loops; (f) a volume comprising at least onesurface, said first and second inductive loops being disposed on the atleast one surface; and (g) a computational function to correlate theeffective magnetic permeability to a presence of said material insidethe volume, wherein said matter is directed to be present between saidfirst and said second inductive loops by an application port, said twoelectrically conductive plates positioned external to said applicationport.